【摘要】：隨著分布式發(fā)電技術(shù)的發(fā)展和直流用電設(shè)備的增多，直流微網(wǎng)成為近年來的研究熱點之一。單向和雙向直流變換器占據(jù)了直流微網(wǎng)中功率變換單元的大部分，因而研究高效率、高功率密度、高可靠性和低成本的直流變換器對提高直流微網(wǎng)性能具有重要的意義。隨著用電設(shè)備功率等級的提高，傳統(tǒng)的單相直流變換器面臨著器件電流應力較高的問題，而采用三相直流變換器成為解決該問題的主要途徑之一。本文主要研究內(nèi)容即是直流微網(wǎng)中單向和雙向運行的三相直流變換器。 首先，本文提出了一種通過傳統(tǒng)不對稱PWM控制，采用Y-Δ連接變壓器的三倍流整流三相全橋直流變換器。該變換器應用于直流微網(wǎng)360V高壓母線向48V低壓母線傳遞能量的場合。本文分析了該變換器的工作原理，討論了橋臂上管和下管實現(xiàn)ZVS的差異，并從磁性元件和功率器件的應力、實現(xiàn)軟開關(guān)的負載范圍等角度與采用Δ-Δ型變壓器的該變換器、移相全橋變換器作了對比，結(jié)果表明本文提出的變換器能降低開關(guān)器件的電流應力、且具有更寬范圍的ZVS負載范圍。 其次，本文針對該三相直流變換器，提出了一種新型PWM控制方式，使得變換器能夠雙向運行，有效占空比范圍得以拓寬，且可以提升1倍的電壓變比，因而可以減小變壓器匝比以降低漏感，特別適合于直流微網(wǎng)中高壓直流母線與儲能單元之間的高電壓變比、能量雙向流動的功率變換場合。新型PWM控制方式下該變換器具有兩種工作模式，本文從器件應力、損耗分析等方面進行了對比，，給出了該變換器的設(shè)計準則。 最后，針對本文提出的兩種控制方式下的三相直流變換器，分別設(shè)計了一臺2kW的原理樣機進行實驗驗證。實驗結(jié)果表明，該變換器采用傳統(tǒng)PWM方式控制時，可以實現(xiàn)所有開關(guān)管的ZVS，輸出電流紋波脈動大大減�。徊捎眯滦蚉WM方式控制時，該變換器可以提高1倍電壓變比，能量可以雙向流動。
[Abstract]:With the development of distributed generation technology and the increase of DC power equipment, DC microgrid has become one of the research hotspots in recent years. Unidirectional and bidirectional DC / DC converters account for the majority of power conversion units in DC microgrids, so it is important to study high efficiency, high power density, high reliability and low cost DC / DC converters for improving DC microgrid performance. With the improvement of power level of electrical equipment, the traditional single-phase DC / DC converter is faced with the problem of high current stress of the device, and the adoption of three-phase DC / DC converter is one of the main ways to solve this problem. The main research content of this paper is three-phase DC-DC converter in DC micro-grid running in one-way and two-way. Firstly, this paper presents a three-phase full-bridge DC / DC converter with triple-current rectifier using Y- 螖 connected transformer through traditional asymmetric PWM control. The converter is used to transfer energy from 360V high voltage bus to 48V low voltage bus. In this paper, the working principle of the converter is analyzed, the difference between the upper tube of the bridge arm and the lower tube in realizing ZVS is discussed. From the angle of the stress of the magnetic element and power device, the load range of the soft switch and the converter using 螖-螖 type transformer, the converter is discussed. The results show that the proposed converter can reduce the current stress of switching devices and has a wider range of ZVS loads. Secondly, a new type of PWM control method is proposed for the three-phase DC / DC converter, which enables the converter to operate in both directions, widen the effective duty cycle range, and increase the voltage change ratio by twice. Therefore, the turn ratio of transformer can be reduced to reduce leakage inductance, which is especially suitable for the high voltage ratio between HVDC bus and energy storage unit in DC microgrid, and for the power conversion of bidirectional energy flow. The converter has two operating modes under the new PWM control mode. In this paper, the design criteria of the converter are compared in terms of device stress and loss analysis. Finally, an experimental prototype of 2kW is designed for the three phase DC / DC converter with two control modes proposed in this paper. The experimental results show that the ripple of the ZVS, output current can be greatly reduced when the converter is controlled by traditional PWM mode, and the voltage variation ratio of the converter can be increased by 1 times when the converter is controlled by a new PWM mode. Energy can flow in both directions.
【學位授予單位】：南京航空航天大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：TM46

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